Porphyromonas endodontalis-Like Organisms from Extraoral Sources

Porphyromonas endodontalis has been isolated almost exclusively from the oral cavity. P. endodontalis is a key pathogen in endodontic infections such as infected root canals and abscesses [1]. We report herein the isolation of P. endodontalis-like organisms (PELOs) from extraoral sources. These organisms have a close phenotypic resemblance to oral isolates of P. endodontalis; however, their taxonomic position warrants reassessment. The aim of this study was to describe the isolation and characterization of PELOs and the laboratory tests useful in their identification. Six PELO isolates recovered in fecal specimens from young children, as well as six strains that originated from extraoral clinical specimens from adult patients (from the Wadsworth Anaerobic Bacteriology Laboratory [WAL; West Los Angeles, CA] collection) and P. endodontalis ATCC (American Type Culture Collection) 35406T, were included in the bacteriologic study. Five other P. endodontalis strains isolated from oral sources, five Porphyromonas asaccharolytica strains, and P. asaccharolytica ATCC 25260T were also included in the cellular-fatty-acid analyses (table 1). The fecal strains were isolated during a microbiological study of antimicrobial agent-associated flora changes. The fecal samples were inoculated on various selective and nonselective media with use of quantitative culture techniques [2]. To isolate PELOs, we used Brucella blood agar and kanamycin/vancomycin laked blood (KVLB) agar and phenylethyl alcohol (PEA) blood agar plates incubated anaerobically for 5-10 days. The clinical WAL strains were characterized during a comprehensive reevaluation of pigmented gram-negative rods. We characterized the strains by using routine biochemical tests [2], special-potency antibiotic identification disks, prereduced anaerobically sterilized biochemicals, gas liquid chromatography, API ZYM (bioMerieux, Marcy l'Etoile, France) panels, and Rosco Diagnostic Tablets (Rosco, Taastrup, Denmark). The production of /-lactamase was detected with use of the nitrocefin disk test (Nitrocefin, BIODISK, Solna, Sweden). Cellular fatty acids were detected by a Hewlett Packard (Palo Alto, CA) 5890 series II gas chromatograph and the Microbial Identification System software (Microbial ID, Newark, DE). The isolates were grown on supplemented brain heart infusion agar with blood, and the bacterial mass was harvested directly from the plates because of poor growth in liquid media. The corresponding library (Microbial ID, ANAEROBE version 3.8) was used in successive analyses. The identity of fatty acids was confirmed by combined gas chromatographymass spectrometry. A cluster analysis, expressed as a dendrogram, was run by the program included in the MIDI software. The sources of PELOs in clinical specimens were appendiceal tissue or peritoneal fluid (three specimens), an infected sacral de-